Battery with acidified cathode and lithium anode

ABSTRACT

A battery comprising an acidified metal oxide (“AMO”) material, preferably in monodisperse nanoparticulate form 20 nm or less in size, having a pH&lt;7 when suspended in a 5 wt % aqueous solution and a Hammett function H0&gt;−12, at least on its surface.

CROSS-REFERENCE TO RELATED CASE

This application claims the benefit of U.S. provisional patentapplication Ser. No. 62/507,659, filed on May 17, 2017, entitled“Battery with Acidified Cathode and Lithium Anode,” and incorporatessuch provisional application by reference into this disclosure as iffully set out at this point.

FIELD

This disclosure is in the field of materials useful in chemical energystorage and power devices such as, but not limited to, batteries. Morespecifically, this disclosure relates to a battery cell with a cathodeand/or an anode comprising acidified metal oxide (“AMO”) nanomaterials.In some embodiments, a battery cell is constructed with an AMO cathodeand an anode consisting substantially of elemental lithium.

BACKGROUND OF THE INVENTION

Metal oxides are compounds in which oxygen is bonded to metal, having ageneral formula M_(m)O_(x). They are found in nature but can beartificially synthesized. In synthetic metal oxides the method ofsynthesis can have broad effects on the nature of the surface, includingits acid/base characteristics. A change in the character of the surfacecan alter the properties of the oxide, affecting such things as itscatalytic activity and electron mobility. The mechanisms by which thesurface controls reactivity, however, are not always well characterizedor understood. In photocatalysis, for example, the surface hydroxylgroups are thought to promote electron transfer from the conduction bandto chemisorbed oxygen molecules.

Despite the importance of surface characteristics, the metal oxideliterature, both scientific papers and patents, is largely devoted tocreating new, nanoscale, crystalline forms of metal oxides for improvedenergy storage and power applications. Metal oxide surfacecharacteristics are ignored and, outside of the chemical catalysisliterature, very little innovation is directed toward controlling oraltering the surfaces of known metal oxides to achieve performancegoals.

The chemical catalysis literature is largely devoted to the creation of“superacids”—acidity greater than that of pure sulfuric acid (18.4 MH₂SO₄)—often used for large-scale reactions such as hydrocarboncracking. Superacidity cannot be measured on the traditional pH scale,and is instead quantified by Hammet numbers. Hammet numbers (H₀) can bethought of as extending the pH scale into negative numbers below zero.Pure sulfuric acid has an H₀ of −12.

There are, however, many reaction systems and many applications forwhich superacidity is too strong. Superacidity may, for example, degradesystem components or catalyze unwanted side reactions. However, aciditymay still be useful in these same applications to provide enhancedreactivity and rate characteristics or improved electron mobility.

The battery literature teaches that acidic groups are detrimental inbatteries, where they can attack metal current collectors and housingsand cause deterioration in other electrode components. Further, theprior art teaches that an active, catalytic electrode surface leads toelectrolyte decomposition which can result in gas generation within thecell and ultimately in cell failure.

A need exists for battery implementation having a synthetic metal oxidethat is acidic but not superacidic at least on its surface and isdeployed within the anode and/or cathode. Further, existing batteryconstruction techniques should be updated to take full advantage of thenew materials available according to the present disclosure as well aspreviously known materials.

SUMMARY OF THE INVENTION

This application describes materials corresponding to acidified metaloxides (“AMO”) and applications for using the AMOs, including inbatteries, such as in battery electrode materials, as catalysts, asphotovoltaic or photoactive components, and sensors. Techniques forpreparing AMOs and devices comprising AMOs are further disclosed. Thedisclosed AMOs are optionally used in combination with acidic species toenhance their utility.

This application further describes high capacity electrochemical cellsincluding electrodes comprising a metal oxide. Techniques for preparingmetal oxides and electrochemical cells comprising metal oxides arefurther disclosed. Optionally, the disclosed metal oxides are used inconjunction with conductive materials to form electrodes. The formedelectrodes are useful with metallic lithium and conventional lithium ionelectrodes as the corresponding counter electrodes. The disclosed metaloxides are optionally used in combination with acidic species to enhancetheir utility.

The AMOs described include those in the form of a nanomaterial, such asa nanoparticulate form, which may be monodispersed or substantiallymonodispersed and have particle sizes less than 100 nm, for example. Thedisclosed AMOs exhibit low pH, such as less than 7 (e.g., between 0 and7), when suspended in water or resuspended in water after drying, suchas at a particular concentration (e.g., 5 wt. %), and further exhibit aHammett function, H0, that is greater than −12 (i.e., not superacidic),at least on the surface of the AMO.

The surface of the AMOs may optionally be functionalized, such as byacidic species or other electron withdrawing species. Synthesis andsurface functionalization may be accomplished in a “single-pot”hydrothermal method in which the surface of the metal oxide isfunctionalized as the metal oxide is being synthesized from appropriateprecursors. In some embodiments, this single-pot method does not requireany additional step or steps for acidification beyond those required tosynthesize the metal oxide itself, and results in an AMO material havingthe desired surface acidity (but not superacidic).

Optionally, surface functionalization occurs using strongelectron-withdrawing groups (“EWGs”)—such as SO₄, PO₄, or halogens (Br,Cl, etc.)—either alone or in some combination with one another. Surfacefunctionalization may also occur using EWGs that are weaker than SO₄,PO₄, or halogens. For example, the synthesized metal oxides may besurface-functionalized with acetate (CH₃COO), oxalate (C₂O₄), andcitrate (C₆H₅O₇) groups.

Despite the conventional knowledge that acidic species are undesirablein batteries because they can attack metal current collectors andhousings and cause deterioration in other electrode components, and thatactive, catalytic electrode surfaces can lead to electrolytedecomposition, gas generation within the cell, and ultimately in cellfailure, the inventors have discovered that acidic species andcomponents can be advantageous in batteries employing AMO materials inbattery electrodes.

For example, the combination or use of the AMO with acidic species canenhance the performance of the resultant materials, systems or devices,yielding improved capacity, cyclability, and longevity of devices. As anexample, batteries employing AMO materials in combination with acidicelectrolytes or electrolytes containing acidic species as describedherein exhibit considerable gains in capacity, such as up to 100 mAh/gor more greater than similar batteries employing non-acidifiedelectrolytes or electrolytes lacking acidic species. In someembodiments, improvements in capacity between 50 and 300 mAh/g may beachieved. In addition, absolute capacities of up to 1000 mAh/g or moreare achievable using batteries having acidified electrolytes orelectrolytes including acidic species. Moreover, cycle life of a batterymay be improved through the use of acidic electrolytes or electrolytescontaining acidic species, such as where a battery's cycle life isextended by up to 100 or more charge-discharge cycles.

In addition or alternatively, batteries including an electrode, such asa cathode or anode, that is itself acidic or that includes acidicspecies, such as an organic acid, may also be beneficial and, again,contrary to the conventional teaching in battery technology. Forexample, batteries incorporating acidic electrodes or acidic specieswithin the electrode may enhance the performance and yield improvedcapacity, cyclability, and longevity, particularly when used inelectrodes including AMO materials. Capacity gains of up to 100 mAh/g orgreater are achievable. Cycle life of a battery may also be improvedthrough the use of acidic electrodes or electrodes containing acidicspecies, such as where a battery's cycle life is extended by up to 100or more cycles. As an example, an acidic electrode or an electrode thatincludes acidic species may exhibit a pH less than 7 (but not besuperacidic), such as when components of the electrode are suspended inwater (or resuspended in water after drying) at 5 wt. %.

Electrodes corresponding to the present disclosure may comprises alayered structure including a first set of layers comprising aconductive material and a second set of layers comprising the metaloxide, such as an acidified metal oxide (AMO) nanomaterial. Optionally,the first set of layers and the second set of layers may be provided inan alternating configuration. Optionally, the first set of layers andthe second set of layers independently comprises between 1 and 20layers. Optionally, the first set of layers and the second set of layersindependently have thicknesses of between 1 μm and 50 μm, between 2 μmand 25 μm, between 3 μm and 20 μm, between 4 μm and 15 μm, or between 5μm and 10 μm. Optionally, the metal oxide comprises between 5 and 90weight percent of the second set of layers, such as 5, 10, 15, 20, 25,30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90 weight percent.Optionally, the conductive material and the binder each independentlycomprise between 5 and 90 weight percent of the first set of layers suchas 25, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85,or 90 weight percent.

A first electrode optionally comprises the metal oxide at up to 95weight percent of the first electrode, up to 80 weight percent of thefirst electrode, up to 70 weight percent of the first electrode, between1 and 50 weight percent of the first electrode, between 1 and 33 weightpercent of the first electrode, between 15 and 25 weight percent of thefirst electrode, between 55 and 70 weight percent of the firstelectrode, between 20 and 35 weight percent of the first electrode,between 5 and 15 weight percent of the first electrode. Specificexamples of metal oxide weight percents for the first electrode include1%, 5%, 11%, 12%, 13%, 14%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%,30%, 31%, 32%, 33%, 60%, 61%, 62%, 63%, 64%, 65%, etc. Optionally, theconductive material and the binder each independently comprise themajority of the remainder of the first electrode. For example, theconductive material and the binder each independently comprise between10 and 74 weight percent of the first electrode. Optionally, theconductive material and the binder each together comprise between 20 and90 weight percent of the first electrode. Optionally, the AMOnanomaterial is added as a dopant of 1-10% by weight to a conventionallithium ion electrode, such as graphite, lithium cobalt oxide, etc.

Various materials are useful for the electrodes described herein.Example metal oxides include, but are not limited to, a lithiumcontaining oxide, an aluminum oxide, a titanium oxide, a manganeseoxide, an iron oxide, a zirconium oxide, an indium oxide, a tin oxide,an antimony oxide, a bismuth oxide, or any combination of these.Optionally, the oxides are in the form of an AMO. As described herein,the metal oxide optionally comprises and/or is surface functionalized byone or more electron withdrawing groups selected from Cl, Br, BO3, SO4,PO4, NO3, CH3COO, C2O4, C2H2O4, C6H8O7, or C6H5O7. Example conductivematerial comprises one or more of graphite, conductive carbon, carbonblack, Ketjenblack, or conductive polymers, such aspoly(3,4-ethylenedioxythiophene) (PEDOT), polystyrene sulfonate (PSS),PEDOT:PSS composite, polyaniline (PANI), or polypyrrole (PPY).

In some embodiments, electrodes comprising AMO nanomaterials are used inconjunction with other electrodes to form a cell. For example, a secondelectrode of such a cell may comprise graphite, metallic lithium, sodiummetal, lithium cobalt oxide, lithium titanate, lithium manganese oxide,lithium nickel manganese cobalt oxide (NMC), lithium iron phosphate,lithium nickel cobalt aluminum oxide (NCA), an AMO nanomaterial, or anycombination of these. In a specific embodiment, the first electrodecomprises an AMO of SnO2, and the second electrode comprises metalliclithium.

Various materials are useful for the electrodes described herein.Example metal oxides include, but are not limited to, a lithiumcontaining oxide, an aluminum oxide, a titanium oxide, a manganeseoxide, an iron oxide, a zirconium oxide, an indium oxide, a tin oxide,an antimony oxide, a bismuth oxide, or any combination of these.Optionally, the oxides are in the form of an AMO. As described herein,the metal oxide optionally comprises and/or is surface functionalized byone or more electron withdrawing groups selected from Cl, Br, BO3, SO4,PO4, NO3, CH3COO, C2O4, C2H2O4, C6H8O7, or C6H5O7. Example, conductivematerial comprises one or more of graphite, conductive carbon, carbonblack, Ketjenblack, or conductive polymers, such aspoly(3,4-ethylenedioxythiophene) (PEDOT), polystyrene sulfonate (PSS),PEDOT:PSS composite, polyaniline (PANI), or polypyrrole (PPY).

As a further example, batteries in which the electrode is formed using aslurry may also be beneficial and contrary to the conventional teachingin battery technology. As described herein, the AMO material mayoptionally formed into battery electrode by first forming a slurry ofthe AMO material with one or more binder compounds, solvents, additives(e.g., conductive additives or acidic additives), and/or other wetprocessing materials. The slurry may be deposited on a conductivematerial or current collector in order to form an electrode. Such aslurry and/or a solvent may optionally be acidic or include acidicspecies and, again, allow for improvements in capacity, cyclability, andlongevity of the resultant battery. Optionally, all or a portion of thesolvent may be evaporated, leaving the AMO material, binder, additives,etc. The resultant material may optionally exhibit its own acidity, suchhaving a pH less than 7 (but not superacidic), when suspended in water(or resuspended in water after drying) at 5 wt. %, for example.

Various techniques may be used for making the metal oxide. Optionally,making a metal oxide comprises forming a solution comprising a metalsalt, ethanol, and water; acidifying the solution by adding an acid tothe solution; basifying the solution by adding an aqueous base to thesolution; collecting precipitate from the solution; washing theprecipitate; and drying the precipitate.

Optionally, making an electrode further comprises depositing a furtherconductive layer over the electrode layer, such as a conductive layerthat comprises a second conductive material. Optionally, depositing theconductive layer include forming a conductive slurry using the secondconductive material, a second binder, and a second solvent; depositing aconductive slurry layer on the electrode layer; and evaporating at leasta portion of the second solvent to form the conductive layer.Optionally, making an electrode comprises forming 1-20 additionalconductive layers comprising the conductive material and 1-20 additionalelectrode layers comprising the metal oxide. For example, an electrodemay comprise a layered structure including a first set of layerscomprising a second conductive material and a second set of layerscomprising the metal oxide, such as where the first set of layers andthe second set of layers are provided in an alternating configuration.Example layers include those independently having thicknesses of between1 μm and 50 μm. Example layers include those comprising between 10 and90 weight percent of the metal oxide. Example layers include thoseindependently comprising between 5 and 85 weight percent of theconductive material and/or binder.

Electrodes formed using the methods of this aspect may have a metaloxide content of up to 80 weight percent. Electrodes formed using themethods of this aspect may have a conductive material and/or bindercontent of between 10 and 70 weight percent of the electrode.

As described above, acidic species may optionally be included as anadditive to any of the components of a battery, such as an electrode oran electrolyte. Optionally, a battery comprising an AMO may include anelectrolyte positioned between the electrodes in which acidic speciesare dissolved in a solvent. Such an electrolyte may also be referred toherein as an acidified electrolyte. The electrolyte may optionallyinclude one or more lithium salts dissolved in the solvent, such asLiPF₆, LiAsF₆, LiClO₄, LiBF₄, LiCF₃SO₃, and combinations of these. Itwill be appreciated that the electrolyte may be positioned not only inthe space separating the electrodes (i.e., between the electrodes), butmay also penetrate through or into pores of the electrodes and/orthrough or into pores of any materials or structures optionallypositioned between the electrodes, such as a separator.

Example acidic species useful with the AMOs, electrodes, andelectrolytes described herein include but are not limited to organicacids, such as carboxylic acids. Example acidic species include thoseexhibiting a pKa in water of between −10 and 7, between −5 and 6,between 1 and 6, between 1.2 and 5.6, or about 4. Specific exampleorganic acids include, for example, oxalic acid, carbonic acid, citricacid, maleic acid, methylmalonic acid, formic acid, glutaric acid,succinic acid, methylsuccinic acid, methylenesuccinic acid, citraconicacid, acetic acid, benzoic acid. Example organic acids includedicarboxylic acids, such as those having a formula of

where R is a substituted or unsubstituted C1-C20 hydrocarbon, such as asubstituted or unsubstituted alkyl group, a substituted or unsubstitutedalkenyl group, a substituted or unsubstituted aromatic orheteroaromatic, a substituted or unsubstituted amine, etc. Exampleorganic acids also include those having a formula of

where L is a substituted or unsubstituted C1-C20 divalent hydrocarbon,such as a substituted or unsubstituted alkylene group, a substituted orunsubstituted arylene group, a substituted or unsubstitutedheteroarylene group, a substituted or unsubstituted amine, etc. Organicacids may include organic acid anhydrides, such as having a formula of

where R1 and R2 are independently a substituted or unsubstituted C1-C20hydrocarbon, such as a substituted or unsubstituted alkyl group, asubstituted or unsubstituted alkenyl group, a substituted orunsubstituted aromatic or heteroaromatic group, a substituted orunsubstituted amine, etc. Optionally, R1 and R2 can form a ring. Exampleorganic acid anhydrides include any anhydrides of the above mentionedorganic acids. Specific organic acid anhydrides include, but are notlimited to glutaric anhydride, succinic anhydride, methylsuccinicanhydride, maleic anhydride, and itaconic anhydride.

Useful concentrations of the acidic species in either or both theelectrolyte and the AMO electrode include from 0 wt. % to 10 wt. %, 0.01wt. % to 10 wt. %, from 0.1 wt. % to 10 wt. %, from 1 wt. % to 5 wt. %,or from 3 wt. % to 5 wt. %.

Useful solvents include those employed in lithium ion battery systems,for example, such as ethylene carbonate, butylene carbonate, propylenecarbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate,dipropyl carbonate, ethylmethyl carbonate, methylpropyl carbonate,ethylpropyl carbonate, fluoroethylene carbonate and mixtures thereof.Other useful solvents will be appreciated to those skilled in the art.Optionally, when an acidic species and metal salt are dissolved in asolvent to form an electrolyte, the electrolyte itself exhibits anacidic condition (i.e., pH less than 7).

Example binders useful with the batteries and electrodes describedherein include Styrene Butadiene Copolymer (SBR), PolyvinylideneFluoride (PVDF), Carboxy methyl cellulose (CMC), Styrene ButadieneRubber (SBR), acrylonitrile, polyacrylic acid (PAA), polyvinyl alcohol(PVA), polyamide imide (PAI), and any combination of these. Optionally,conductive polymers may be useful as a binder.

Other example additives useful with the AMOs and electrodes describedherein include, but are not limited to conductive additives. Exampleconductive additives include graphite, conductive carbon, carbon black,Ketjenblack, and conductive polymers, such as poly(3,4-ethylenedioxythiophene (PEDOT), polystyrene sulfonate (PSS),PEDOT:PSS composite, polyaniline (PANI), and polypyrrole (PPY).Conductive additives may be present, for example, in an electrode, atany suitable concentration such as at weight percents greater than 0 andas high as 35 wt. %, 40 wt. % or more. Optionally, conductive additivesare present in an electrode at a range of 1 wt. % to 95 wt. %, 1 wt. %to 35 wt. %, 1 wt. % to 25 wt. %, 5 wt. % to 40 wt. %, 10 wt. % to 40wt. %, 15 wt. % to 40 wt. %, 20 wt. % to 40 wt. %, 25 wt. % to 40 wt. %,30 wt. % to 40 wt. %, 35 wt. % to 40 wt. %, 40 wt. % to 45 wt. %, 40 wt.% to 50 wt. %, 40 wt. % to 55 wt. %, 40 wt. % to 60 wt. %, 40 wt. % to65 wt. %, 40 wt. % to 70 wt. %, 40 wt. % to 75 wt. %, 40 wt. % to 80 wt.%, 40 wt. % to 85 wt. %, 40 wt. % to 90 wt. %, or 40 wt. % to 95 wt. %.

Methods of making batteries are also described herein. An example methodof making a battery comprises making an AMO nanomaterial; forming afirst electrode of or comprising the AMO nanomaterial; forming anelectrolyte by dissolving one or more metal salts in a solvent; andpositioning the electrolyte between the first electrode and a secondelectrode. Another example method of making a battery comprises makingan AMO nanomaterial; forming a first electrode of or comprising the AMOnanomaterial and one or more metal salts; and positioning theelectrolyte between the first electrode and a second electrode.

Electrolytes for use in batteries are also disclosed herein. Forexample, the disclosed electrolytes are useful in batteries comprising afirst electrode and a second electrode, such as a first electrode thatcomprises an acidified metal oxide (AMO) nanomaterial. Exampleelectrolytes comprise a solvent and one or more metal salts dissolved inthe solvent. Optionally, an acidic species is dissolved in the solvent,such as an acidic species that is different from the one or more metalsalts.

As described above, a variety of acidic species are useful in thedisclosed electrolytes, such as an acidic species comprising an organicacid and/or an organic acid anhydride. Example organic acids include,but are not limited to, oxalic acid, acetic acid, citric acid, maleicacid, methylmalonic acid, glutaric acid, succinic acid, methylsuccinicacid, methylenesuccinic acid, citraconic acid, or any combination ofthese. Example organic acid anhydrides include, but are not limited toglutaric anhydride, succinic anhydride, methylsuccinic anhydride, maleicanhydride, itaconic anhydride, or any combination of these. Other acidicspecies examples are described above. Useful acidic species include, butare not limited to, those exhibiting a pKa of between −10 and 7, between−5 and 6, between 1 and 6, between 1.2 and 5.6, or about 4. The acidicspecies may optionally be present in the electrolyte at any suitableconcentration, such as from 0.01 wt. % to 10 wt. %, from 0.1 wt. % to 10wt. %, from 1 wt. % to 5 wt. %, or from 3 wt. % to 5 wt. %.

It will be appreciated that lithium metal salts, such as LiPF₆, LiAsF₆,LiClO₄, LiBF4, LiCF₃SO₃, may be useful components of the disclosedacidified electrolytes. Example solvents include, but are not limitedto, ethylene carbonate, butylene carbonate, propylene carbonate,vinylene carbonate, dimethyl carbonate, diethyl carbonate, dipropylcarbonate, ethylmethyl carbonate, methylpropyl carbonate, ethylpropylcarbonate, fluoroethylene carbonate and mixtures thereof. Examplesolvents may be useful in metal ion batteries, such as lithium ionbatteries.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified cutaway view of an example lithium ion batterycell.

FIG. 2 is another simplified cutaway view of a lithium ion battery cellwith the electrolyte substantially contained by the separator.

FIG. 3 is a schematic of a lithium ion battery comprising multiplecells.

FIG. 4 shows differences in the cyclic voltammogram of AMO tin preparedby the method disclosed herein relative to that of commerciallyavailable, non-AMO tin when cycled against Li.

FIG. 5 shows the total reflectance of AMO tin oxide is different thanthat of commercially available, non-AMO tin oxide.

FIG. 6 is X-ray photoelectron spectroscopy (XPS) data showing surfacefunctionalization arising endogenously from the synthesis methoddisclosed herein. Numbers shown are atomic concentrations in %. Thefar-right column lists the corresponding pH of the synthesizednanoparticles as measured when dispersed at 5 wt % in aqueous solution.

FIG. 7 provides electron micrograph images showing differences inmorphology between AMO nanoparticles synthesized under identicalconditions except for the use of a different group forfunctionalization.

FIG. 8 shows the difference in morphology and performance of AMOnanoparticles synthesized under identical conditions except for havingtwo different total reaction times.

FIG. 9 provides representative half-cell data showing differences inbehavior between spherical and elongated (needle-like or rod-like) AMOsupon cycling against lithium.

FIG. 10 provides X-ray photoelectron spectroscopy analysis of thesurface of AMO nanoparticles synthesized using both a strong(phosphorous containing) and weak (acetate) electron withdrawing groupshows greater atomic concentration of phosphorous than of the bondsassociated with acetate groups.

FIG. 11A provides data showing visible light activity degradation datafor different AMOs.

FIG. 11B provides data showing ultraviolet light activity degradationdata for different AMOs.

FIG. 12 is a graph comparing two AMOs, one having higher capacity foruse in a primary (single use) battery application and the other havinghigher cyclability for use in a secondary (rechargeable) batteryapplication.

FIG. 13 provides charge and discharge capacity data and Columbicefficiency data, illustrating that AMOs can result in enhanced batteryperformance, without deterioration of battery components or gasgeneration.

FIG. 14 shows capacity and cycling data for an AMO in standard,acidified, and basified electrolyte systems.

FIG. 15 shows capacity and cycling data for an AMO, and for the same AMOfrom which the acidification was removed by solvent washing.

FIG. 16 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 17 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 18 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 19 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 20 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 21 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 22 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 23 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 24 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 25 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 26 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 27 provides an electron micrograph image of a synthesized materialand data including a plot of measured capacity versus cycle number aswell as a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the synthesized material.

FIG. 28 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 29 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 30 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 31 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 32 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 33 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 34 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 35 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 36 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 37 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 38 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 39 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 40 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 41 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 42 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 43 provides data including a plot of measured capacity versus cyclenumber as well as a plot of the voltage as a function of time duringcycling for a battery cell including an electrode comprising an AMOmaterial.

FIG. 44 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 45 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 46 provides an electron micrograph image of an AMO material anddata including a plot of measured capacity versus cycle number as wellas a plot of the voltage as a function of time during cycling for abattery cell including an electrode comprising the AMO material.

FIG. 47 is a plot of temperature and voltage for a cell constructedaccording to the present disclosure and subjected to a nail penetrationtest.

FIG. 48A is a plot of temperature and voltage for a cell constructedaccording to the present disclosure and subjected to an overcharge test.

FIG. 48B is a plot of the overcharge test of FIG. 48A focusing on thestart of the test.

DEFINITIONS

For the purposes of this disclosure, the following terms have thefollowing meanings:

Acidic oxide—a term used generally in the scientific literature to referto binary compounds of oxygen with a nonmetallic element. An example iscarbon dioxide, CO₂. The oxides of some metalloids (e.g., Si, Te, Po)also have weakly acidic properties in their pure molecular state.

Acidified metal oxide (“AMO”)—a term used here to denote a binarycompound of oxygen with a metallic element which has been synthesized ormodified to have an acidity greater than that of its naturalmineralogical state and also a Hammet function, H₀>−12 (notsuperacidic). The average particle size is also less than that of thenatural mineralogical state. Naturally occurring mineralogical forms donot fall within the scope of the inventive AMO material. A synthesizedmetal oxide, however, that is more acidic than its most abundantnaturally occurring mineralogical form (of equivalent stoichiometry) butnot superacidic falls within the bounds of this disclosure and can besaid to be an AMO material provided it satisfies certain otherconditions discussed in this disclosure.

Acidic—a term used generally in the scientific literature to refer tocompounds having a pH of less than 7 in aqueous solution.

Electron-withdrawing group (“EWG”)—an atom or molecular group that drawselectron density towards itself. The strength of the EWG is based uponits known behavior in chemical reactions. Halogens, for example areknown to be strong EWGs. Organic acid groups such as acetate are knownto be weakly electron withdrawing.

Hammet function—An additional means of quantifying acidity in highlyconcentrated acid solutions and in superacids, the acidity being definedby the following equation: H₀=pK_(BH+)+log([B]/[BH+]). On this scale,pure 18.4 molar H₂SO₄ has a H₀ value of −12. The value H₀=−12 for puresulfuric acid must not be interpreted as pH=−12, instead it means thatthe acid species present has a protonating ability equivalent to H₃O⁺ ata fictitious (ideal) concentration of 10¹² mol/L, as measured by itsability to protonate weak bases. The Hammett acidity function avoidswater in its equation. It is used herein to provide a quantitative meansof distinguishing the AMO material from superacids. The Hammet functioncan be correlated with colorimetric indicator tests and temperatureprogrammed desorption results.

Metal oxide—a term used generally in the scientific literature to referto binary compounds of oxygen with a metallic element. Depending ontheir position in the periodic table, metal oxides range from weaklybasic to amphoteric (showing both acidic and basic properties) in theirpure molecular state. Weakly basic metal oxides are the oxides oflithium, sodium, magnesium, potassium, calcium, rubidium, strontium,indium, cesium, barium and tellurium. Amphoteric oxides are those ofberyllium, aluminum, gallium, germanium, astatine, tin, antimony, leadand bismuth.

Monodisperse—characterized by particles of uniform size which aresubstantially separated from one another, not agglomerated as grains ofa larger particle.

pH—a functional numeric scale used generally in the scientificliterature to specify the acidity or alkalinity of an aqueous solution.It is the negative of the logarithm of the concentration of thehydronium ion [H₃O⁺]. As used here it describes the relative acidity ofnanoparticles suspended in aqueous solution.

Surface functionalization—attachment of small atoms or molecular groupsto the surface of a material.

Superacid—substances that are more acidic than 100% H₂SO₄, having aHammet function, H₀<−12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, a lithium ion battery cell 100 is illustratedin a simplified cutaway view. The cell 100 may comprise a casing orcontainer 102. In some embodiments, the casing 102 is a polymer or analloy. The casing 102 chemically and electrically isolates the contentsof the cell 100 from adjacent cells, from contamination, and fromdamaging or being damaged by other components of the device into whichthe cell 100 is installed. A full battery may contain a plurality ofcells arranged in a series and/or parallel configuration. The batterymay have a further casing or securement mechanism binding the pluralityof cells together as is known in the art.

The cell 100 provides a cathode 104 and an anode 106. The contents ofthe cell 100 undergo a chemical reaction when a conduction path isprovided between the cathode 104 and anode 106 that is external to thecell 100. As a result of the chemical reaction, electrons are providedat the anode 106 that flow to the cathode 104 via the circuit providedexternal to the battery (sometimes referred to as the load). At a basiclevel, during discharge of the cell 100, the materials comprising theanode 106 are oxidized providing the electrons that flow through thecircuit. The materials comprising the cathode 104, as recipient of theelectrons given up by the anode 106, are reduced.

Within the cell 100, during discharge, metallic cations move through anelectrolyte 108 from the anode 106 to the cathode 104. In the case of alithium based battery, the metallic cation may be a lithium cation(Li+). The electrolyte 108 may be a liquid electrolyte such as a lithiumsalt in an organic solvent (e.g., LiClO₄ in ethylene carbonate). Otherlithium based electrolyte/solvent combinations may be used as are knownin the art. In some cases, the electrolyte 108 may be a solidelectrolyte such as a lithium salt in a polyethylene oxide. Optionally,the electrolyte may comprise a polymer electrolyte. Example electrolytesinclude those described in U.S. Patent Application Publication2017/0069931, which is hereby incorporated by reference.

A separator 110 may be employed to prevent contact between theelectrodes 104, 106. The separator 110 may be a porous layer of materialthat is permeable to the lithium ions and the electrolyte 108 but nototherwise electrically conductive so as to prevent internal shorting ofthe cell 100. As is known in the art, the separator 110 may compriseglass fibers or may comprise a polymer, possibly with a semi-crystallinestructure. Additional components, such as current collectors, may alsobe included in the cell 100, but are not shown in FIG. 1.

Together the anode 104, cathode 106, electrolyte 108, and separator 110form the completed cell 100. Since the separator 110 is porous, theelectrolyte 108 may flow into, or be contained by, the separator 110.Under normal operating conditions, the porosity of the separator 110allows for ion (Li+) flow between the electrodes 104, 106 via theelectrolyte 108. As is known in the art, a separator can be constructedso as to melt and close the internal pore structure to shut down thecell in the event of exposure to excess heat or a runaway exothermicreaction.

Most lithium-based cells are so-called secondary batteries. They can bedischarged and recharged many times before the chemical or structuralintegrity of the cell falls below acceptable limits. Cells and batteriesaccording to the present disclosure are considered to be both primary(e.g., single use) and secondary batteries.

In the case of the cell 100 being a secondary cell (or part of asecondary battery) it should be understood that the cell 100 may berecharged either alone or as a component of a completed system whereinmultiple cells are recharged simultaneously (and possibly in the sameparallel or series circuit).

A reverse voltage is applied to the cell 100 in order to effectcharging. It should be understood that various schemes for effectiverecharging of lithium batteries can be employed. Constant current,variable current, constant voltage, variable voltage, partial dutycycles, etc., may be employed. The present disclosure is not intended tobe limited to a particular charging methodology unless stated in theclaims. During charging of cell 100, element 115 represents a voltagesource that is applied between cathode 104 and anode 106 to provideelectrons from cathode 105 to anode 106 and allow chemical reactions totake place. Lithium ions are shuttled from cathode 104 to the anode 106through electrolyte 108 and separator 110.

As examples, cathode 104 or anode 106 may independent comprise an AMOmaterial disclosed herein. For use of an AMO material as a cathode, ananode may correspond to lithium metal or a lithium intercalationmaterial, such as graphite. Optionally, electrolyte 108 may include anacidic species, such as dissolved in an organic solvent with a lithiumsalt. In addition to or alternative to use of an acidic species inelectrolyte 108, an electrode (i.e., cathode 104 or anode 106) mayoptionally comprise an AMO and an acidic species. Oxalic acid is anexemplary acidic species.

Without wishing to be bound by any theory, it is believed that thepresence of acidic species in the cathode 104 or anode 106 and/orelectrolyte 108 improves a surface affinity of the AMO material towardlithium ions, resulting in an improved ability to take up lithium ionsduring discharge and overall improvement to capacity as compared to asimilar cell lacking acidic species or having a basified electrode orelectrolyte (i.e., including basic species). Alternatively oradditionally, the presence of acidic species may allow for additionalactive sites for lithium uptake in cathode 104.

It should be understood that FIG. 1 is not to scale. A shown in FIG. 2,in most applications, the separator 110 occupies most or all of thespace between the electrodes 104, 106 and is in contact with theelectrodes 104, 106. In such case, the electrolyte 108 is containedwithin the separator 110 (but may also intrude into the pores or surfaceof the anode or cathode). FIG. 2 is also not necessarily to scale. Theactual geometry of a cell can range from relatively thin and flatpouches, to canister type constructions, to button cells and others.Cell construction techniques such as winding or bobbin or pin typeassemblies may be used.

Current collectors known in the art and other components (not shown) mayalso be relied upon to form a cell 100 into a commercially viablepackage. Although overall shape or geometry may vary, a cell or batterywill normally, at some location or cross section, contain the electrodes104, 106 separated rather than touching, and have the electrolyte 108and possibly separator 110 between them. Cells may also be constructedsuch that there are multiple layers of anodes and cathodes. Cells may beconstructed such that two cathodes are on opposite sides of a singleanode or vice versa.

A functional or operational battery intended for a specific purpose maycomprise a plurality of cells arranged according to the needs ofparticular application. An example of such a battery is shownschematically in FIG. 3. Here the battery 300 comprises four lithiumcells 100 arranged in series to increase voltage. Capacity can beincreased at this voltage by providing additional stacks of four cells100 in parallel with the stack shown. Different voltages can be achievedby altering the number of cells 100 arranged in series.

A positive electrode 306 may be accessible on the outside of a casing302 of the battery 300. A negative electrode 304 is also provided. Thephysical form factor of the electrodes 304, 306 may vary according toapplication. Various binders, glues, tapes and/or other securementmechanisms (not shown) may be employed within a battery casing 302 tostabilize the other components. Batteries based on lithium technologyare generally operable, rechargeable, and storable in any orientation(if a secondary cell). As discussed above, cells 100 may take on variousdifferent geometric shapes. Thus FIG. 3 is not meant to represent anyparticular physical form factor of the battery 300.

The battery 300 may also comprise various adjunct circuitry 308interposing the positive electrode 308 and the lithium cells 100 withinthe casing 302 of the battery 300. In other embodiments, the adjustcircuitry interposes the negative electrode 304 and the lithium cells100 instead of, or in addition to, interposing the positive electrode306 and the lithium cells 100. The adjunct circuitry 308 may includeshort circuit protection, overcharge protection, overheating shutdownand other circuitry as is known in the art to protect the battery 300,the cells 100, and/or any load attached to the battery 300.

The composition of materials chosen for the cathode 104, anode 106, andelectrolyte may be critical to the performance of the cell 100 and anybattery of which it forms a part. In the context of the presentdisclosure, various examples of AMOs and methods for their productionare provided in this regard. These AMOs are suitable for use in forminganodes or cathodes in half cells, cells, and batteries. The AMOs of thepresent disclosure are otherwise compatible with known lithium celltechnology including existing anode and cathode compositions,electrolyte formulations, and separator compositions.

In the context of the present disclosure, various examples of AMOs andmethods for their production and use are provided. These AMOs aresuitable for use in forming cathodes or anodes in half cells, cells, andbatteries. The disclosed AMOs are otherwise compatible with conventionallithium battery technology, including existing anode compositions,cathode compositions, electrolyte formulations, and separatorcompositions. It will be appreciated that the material of the anode 106chosen for a cell or battery according to the present disclosure may beless electronegative than the material of the cathode to suitablycomplement the cathodic materials. In one particular embodiment, thedisclosed AMOs are useful as a cathode in a cell having a metalliclithium anode.

In various embodiments of the present disclosure, the cathode 104comprises an AMO material having a surface that is acidic but notsuperacidic. This would be in contrast to materials previously known andutilized as cathodes such as lithium cobalt or lithium manganesematerials. The AMO materials of the present disclosure and methods fortheir production are described below. In other embodiments, the anode106 comprises an AMO material of the present disclosure having a surfacethat is acidic but not super acidic.

The surfaces of metal oxides are ideally arrays of metal and oxygencenters, ordered according to the crystalline structure of the oxide. Inreality the arrays are imperfect, being prone to vacancies, distortion,and the effects of surface attachments. Regardless, any exposed metalcenters are cationic (positively charged) and can accept electrons, thusfunctioning by definition as Lewis acid sites. Oxygen centers areanionic (negatively charged) and act as Lewis base sites to donateelectrons. This leads to the well-known amphotericity of metal oxidesurfaces.

Under normal atmospheric conditions, the presence of water vapor willadsorb to the metal oxide surface either molecularly (hydration) ordissociatively (hydroxylation). Both OH− and H+ species can adsorb onthe oxide surface. The negatively-charged hydroxyl species will attachat the metal, cationic (Lewis acid, electron accepting) centers, and theH+ will attach at the oxygen, anionic (Lewis base, electron donating)centers. Both adsorptions lead to the presence of the same functionalgroup—a hydroxyl—on the metal oxide surface.

These surface hydroxyl groups can serve as either Brønsted acids or asBrønsted bases, because the groups can either give up or accept aproton. The tendency of an individual hydroxyl group to be a protondonor or a proton acceptor is affected by the coordination of the metalcation or oxygen anion to which it is attached. Imperfections of themetal oxide surface such as oxygen vacancies, or coordination of thesurface groups with other chemical species, mean that all cations andanions are not equally coordinated. Acid-base sites will vary in numberand in strengths. When broadly “totaled” across the surface of theoxide, this can give the surface an overall acidic or basic character.

The quantity and strength of Lewis acid and base sites (from the exposedmetal cations and oxygen anions, respectively) and Brønsted acid andbase sites (from the surface hydroxyl groups)—add broad utility andfunctionality to the metal oxide and its use in both chemical reactionsand device applications. The sites are a strong contributor to thechemical reactivity of the metal oxide. They can serve as anchor sitesto which other chemical groups, and even additional metal oxides, may beattached. And they can affect surface charge, hydrophilicity andbiocompatibility.

One way of altering the surface of metal oxides is to attach smallchemical groups or electron-withdrawing groups (“EWGs”) in a processknown as surface functionalization. The EWG induces polarization of thehydroxide bonds and facilitates dissociation of hydrogen. For example, astronger EWG should lead to a more polarized bond and therefore a moreacidic proton. The acidity of Lewis sites can be increased by inducingpolarization that facilitates the donation of electrons to the site.When compounds so made are placed in water, the acidic protons willdissociate and so reduce the aqueous pH measurement.

Though somewhat imprecise when working with solid acid/base systemsrather than liquid ones, traditional methods of pH measurement utilizingtitrations, pH paper and pH probes can be used to evaluate the acidityof metal oxides dispersed in aqueous solution. These measurements can besupplemented by the use of techniques including but not limited tocolorimetric indicators, infrared spectroscopy, and temperatureprogrammed desorption data to establish the acidified nature of themetal oxide surface. Surface groups can be examined by standardanalytical techniques including but not limited to x-ray photoelectronspectroscopy.

Surface functionalization can be accomplished post-synthesis, includingbut not limited to exposing the metal oxide to acidic solutions or tovapors containing the desired functional groups. It can also beaccomplished via solid state methods, in which the metal oxide is mixedand/or milled with solids containing the desired functional groups.However, all of these methods require an additional surfacefunctionalization step or steps beyond those required to synthesize themetal oxide itself.

Synthesis and surface functionalization of the AMO material may beaccomplished in a “single-pot” hydrothermal synthesis method or itsequivalent in which the surface of the metal oxide is functionalized asthe metal oxide is being synthesized from appropriate precursors. Aprecursor salt containing an EWG is solubilized and the resultingsolution is acidified using an acid containing a second EWG. Thisacidified solution is then basified and the basified solution is heatedthen washed. A drying step produces the solid AMO material.

By way of example, a preferred embodiment of an AMO form of tin oxidewas synthesized and simultaneously surface functionalized using thefollowing single-pot method:

-   -   1. Initially, seven grams (7 g) of a tin (II) chloride dihydrate        (SnCl₂2H₂O) is dissolved in a solution of 35 mL of absolute        ethanol and 77 mL distilled water.    -   2. The resulting solution is stirred for 30 minutes.    -   3. The solution is acidified by the addition of 7 mL of 1.2 M        HCl, added dropwise, and the resulting solution is stirred for        15 minutes.    -   4. The solution is basified by the addition of 1 M of an aqueous        base, added dropwise until the pH of the solution is about 8.5.    -   5. The resulting opaque white suspension is then placed in a        hot-water bath (˜60° to 90° C.) for at least 2 hours while under        stirring.    -   6. The suspension is then washed with distilled water and with        absolute ethanol.    -   7. The washed suspension is dried at 100° C. for 1 hour in air        and then annealed at 200° C. for 4 hours in air.

This method results in an AMO of tin, surface-functionalized withchlorine, whose pH is approximately 2 when resuspended and measured inan aqueous solution at 5 wt % and room temperature. By definition itsHammet function, H₀>−12. Although an open system such as a flask isdescribed here, a closed system such as an autoclave may also be used.

Utilizing the single pot method disclosed above, a number of AMO's havebeen synthesized. Table 1 below describes the precursors and acids thathave been used. In some instances, a dopant is utilized as well:

Precursor Dopant Acid SnAc CH₃COOH SnAc H₂SO₄ SnAc HNO₃ SnAc H₃PO₄ SnAcC₆H₈O₇ SnAc C₂H₂O₄ SnAc FeAc HCl SnAc FeAc H₂SO₄ SnAc FeAc HNO3 SnAcFeAc C₂H₂O₄ SnAc FeAc H₃PO₄ SnAc FeAc C₆H₈O₇ SnAc HBr SnAc H₃BO₃ SnSO₄MnCl₂ H₂SO₄ SnCl₂ MnCl₂ HCl SnCl₂ FeCl₃ & AlCl₃ HCl FeCl₃ SnCl₂ HClFe(NO₃)₃ HNO₃ BiCl₃ HCl Zr(SO₄)₂ H₂SO₄ TiOSO₄ H₂SO₄ Sb₂(SO₄)₃ H₂SO₄In(Cl)₃ HCl In₂(SO₄)₃ H₂SO₄ In(III)Br HBr InCl₃ HCl LiAc & FeCl₃ SnCl₂HCl where Ac is an acetate group with the chemical formula C₂H₃O₂

In some embodiments, the electron withdrawing groups have a carbon chainlength of 6 or less and/or an organic mass or 200 or less (AMU). In someembodiments, the electron withdrawing groups have a carbon chain lengthor 8 or less, or 10 or less, and/or an organic mass of 500 or less.

It will be appreciated that the method's parameters can be varied. Theseparameters include, but are not limited to, type and concentration ofreagents, type and concentration of acid and base, reaction time,temperature and pressure, stir rate and time, number and types ofwashing steps, time and temperature of drying and calcination, and gasexposure during drying and calcination. Variations may be conductedsingly, or in any combination, possibly using experimental designmethodologies. Additionally, other metal oxide synthesis methods—e.g.,spray pyrolysis methods, vapor phase growth methods, electrodepositionmethods, solid state methods, and hydro- or solvo thermal processmethods—may be useful for achieving the same or similar results as themethod disclosed here.

A variety of annealing conditions are useful for preparing AMOnanomaterial. Example annealing temperatures may be below 300° C., suchas from 100° C. to 300° C. Example annealing time may range from about 1hours to about 8 hours, or more. Annealing may take place under avariety of atmospheric conditions. For example, annealing may occur inair at atmospheric pressure. Annealing may occur at elevated pressure(greater than atmospheric pressure) or reduced pressure (less thanatmospheric pressure or in a vacuum). Annealing may alternatively occurin a controlled atmosphere, such as under an inert gas (e.g., nitrogen,helium, or argon) or in the presence of an oxidizing gas (e.g., oxygenor water).

A variety of drying conditions are useful for preparing AMOnanomaterials. Example drying temperatures may be from 50° C. to 150° C.Example drying time may range from about 0.5 hours to about 8 hours, ormore. Drying may take place under a variety of atmospheric conditions.For example, drying may occur in air at atmospheric pressure. Drying mayoccur at elevated pressure (greater than atmospheric pressure) orreduced pressure (less than atmospheric pressure or in a vacuum). Dryingmay alternatively occur in a controlled atmosphere, such as under aninert gas (e.g., nitrogen, helium, or argon) or in the presence of anoxidizing gas (e.g., oxygen or water).

The performance characteristics of the AMO nanomaterials of the presentdisclosure differ from those of non-acidified metal oxide nanoparticles.As one example, FIG. 4 shows differences in the cyclic voltammogram ofAMO tin prepared by the single-pot method relative to that ofcommercially available, non-AMO tin when cycled against lithium. Forexample, the surface-functionalized AMO material exhibits betterreversibility than the non-AMO material. The presence of distinct peaksin the CV of the AMO material may indicate that multiple electrontransfer steps are occurring during charging/discharging. For example, apeak at higher voltage may indicate direct oxidation/reduction of theAMO material, while a peak at lower voltage may originate due tochanging the material structure of the AMO material (i.e., alloying).

As another example, FIG. 5 shows the total reflectance of AMO tin oxideis different than that of commercially available, non-AMO tin oxide. Thedata indicates that the AMO has a lower band gap and therefore moredesirable properties as a component of a photovoltaic system in additionto use as an anode according to the present disclosure.

The AMO material may be thought of as having the general formulaM_(m)O_(x)/Gwhere

-   -   M_(m)O_(x) is the metal oxide, m being at least 1 and no greater        than 5, x being at least 1 and no greater than 21;    -   G is at least one EWG that is not hydroxide, and    -   / simply makes a distinction between the metal oxide and the        EWG, denoting no fixed mathematical relationship or ratio        between the two.        G may represent a single type of EWG, or more than one type of        EWG.

Exemplary AMOs are acidified tin oxides (SnxO_(y)), acidified titaniumdioxides (Ti_(a)O_(b)), acidified iron oxides (Fe_(c)O_(d)), andacidified zirconium oxide (Zr_(e)O_(f)). Exemplary electron-withdrawinggroups (“EWGs”) are Cl, Br, BO₃, SO₄, PO₄ and CH₃COO. Regardless of thespecific metal or EWG, according to the present disclosure, the AMOmaterial is acidic but not superacidic, yielding a pH<7 when suspendedin an aqueous solution at 5 wt % and a Hammet function, H₀>−12, at leaston its surface.

The AMO material structure may be crystalline or amorphous (or acombination thereof), and may be utilized singly or as composites incombination with one another, with non-acidified metal oxides, or withother additives, binders, or conductive aids known in the art. In otherwords, an anode prepared to take advantage of the AMO's of the presentdisclosure may or may not comprise other materials. In one embodiment,the AMO may be layered upon a conductive material to form the cathode104. In some embodiments, the AMO material is added to a conductive aidmaterial such as graphite or conductive carbon (or their equivalents) ina range of 10 wt % to 80 wt % and upwards of 90 wt % to 95 wt %. Inpreferred embodiments, the AMO was added at 10 wt %, 33 wt %, 50 wt %,and 80 wt %.

To maximize the amount of overall surface area available, the AMO shouldbe in nanoparticulate form (i.e., less than 1 micron in size) andsubstantially monodispersed. More preferably, the nanoparticulate sizeis less than 100 nm and, even more preferably, less than 20 nm or 10 nm.

Mixed-metal AMOs, in which another metal or metal oxide is present inaddition to the simple, or binary oxide, have been reduced to practicein forming anodes utilized in half cells, cells, and batteries. Thesemixed-metal AMOs may be thought of as having the general formulaM_(m)N_(n)O_(x)/G and M_(m)N_(n)R_(r)O_(x)/Gwhere:

-   -   M is a metal and m is at least 1 and no greater than 5;    -   N is a metal and n is greater than zero and no greater than 5;    -   R is a metal and r is greater than zero and no greater than 5;    -   O is total oxygen associated with all metals and x is at least 1        and no greater than 21;    -   / simply makes a distinction between the metal oxide and the        electron-withdrawing surface group, denoting no fixed        mathematical relationship or ratio between the two; and    -   G is at least one EWG that is not hydroxide.        G may represent a single type of EWG, or more than one type of        EWG.

Some prior art mixed metal oxide systems, of which zeolites are the mostprominent example, display strong acidity even though each simple oxidedoes not. Preferred embodiments of the mixed-metal AMO of thisdisclosure differ from those systems in that any embodiment must includeat least one AMO which is acidic (but not superacidic) in simpleM_(m)O_(x)/G form. Preferred mixed metal and metal oxide systems areSn_(x)Fe_(c)O_(y+d) and Sn_(x)Ti_(a)O_(y+b), where y+d and y+b may be aninteger or non-integer value.

In another embodiment, the mixed metal AMO material is produced via thesingle-pot method with one modification: synthesis begins with two metalprecursor salts rather than one, in any proportion. For example, Step 1of the single-pot method may be altered as follows: Initially, 3.8 g oftin (II) chloride dihydrate (SnCl₂2H₂O) and 0.2 g of lithium chloride(LiCl) are dissolved in a solution of 20 mL of absolute ethanol and 44mL distilled water.

Metal precursor salts as shown in Table 1 could also be used, in anyproportion. The metal precursor salts could have the same or differinganionic groups, depending on the desired product; could be introduced atdifferent points in the synthesis; or could be introduced as solids orintroduced in a solvent. In some embodiments, a first metal precursorsalt may be used for the primary structure (i.e., larger proportion) ofthe resultant AMO, and a second (and optionally a third) metal precursorsalt may be added as a dopant or as a minor component for the resultantAMO.

Experimentation with the single-pot method led to seven notablefindings. First, in all cases both surface functionalization and acidityarise endogenously (see FIG. 6), rather than created post-synthesis.Unlike prior art surface functionalization methods, the single-potmethod does not require any additional step or steps for surfacefunctionalization beyond those required to synthesize the metal oxideitself, nor does it make use of hydroxyl-containing organic compounds orhydrogen peroxide.

Second, the method is broadly generalizable across a wide range of metaloxides and EWGs. Using the methods of the present disclosure, metaloxides of iron, tin, antimony, bismuth, titanium, zirconium, manganese,and indium have been synthesized and simultaneouslysurface-functionalized with chlorides, sulfates, acetates, nitrates,phosphates, citrates, oxalates, borates, and bromides. Mixed metal AMOsof tin and iron, tin and manganese, tin and manganese and iron, tin andtitanium, indium and tin, antimony and tin, aluminum and tin, lithiumand iron, and lithium and tin also have been synthesized. Additionally,surface functionalization can be accomplished using EWGs that are weakerthan halogens and SO₄ yet still produce acidic but not superacidicsurfaces. For example, the method also has been used to synthesize AMOssurface-functionalized with acetate (CH₃COO), oxalate (C₂O₄), andcitrate (C₆H₅O₇). A variety of Examples are described below.

Third, there is a synergistic relationship between the EWG and otherproperties of the nanoparticles such as size, morphology (e.g.,plate-like, spherical-like, needle- or rod-like), oxidation state, andcrystallinity (amorphous, crystalline, or a mixture thereof). Forexample, differences in morphology can occur between AMO nanoparticlessynthesized under identical conditions except for the use of a differentEWG for surface functionalization (see FIG. 7). The surfacefunctionalization may act to “pin” the dimensions of the nanoparticles,stopping their growth. This pinning may occur on only one dimension ofthe nanoparticle, or in more than one dimension, depending upon exactsynthesis conditions.

Fourth, the character of the AMO is very sensitive to synthesisconditions and procedures. For example, differences in morphology andperformance of the AMO's nanoparticles can occur when synthesized underidentical conditions except for having two different total reactiontimes (see FIGS. 8 & 9). Experimental design methodologies can be usedto decide the best or optimal synthesis conditions and procedures toproduce a desired characteristic or set of characteristics.

Fifth, both the anion present in the precursor salt and the anionpresent in the acid contribute to the surface functionalization of theAMO. In one preferred embodiment, tin chloride precursors andhydrochloric acid are used in a synthesis of an AMO of tin. Theperformance of these particles differ from an embodiment in which tinchloride precursors and sulfuric acid are used, or from an embodiment inwhich tin sulfate precursors and hydrochloric acid are used. Therefore,matching the precursor anion and acid anion is preferred in someembodiments.

Sixth, when utilizing a precursor with a weak EWG and an acid with astrong EWG, or vice versa, the strongly withdrawing anion will dominatethe surface functionalization. This opens up a broader range ofsynthesis possibilities, allowing functionalization with ions that arenot readily available in both precursor salts and acids. It may alsopermit mixed functionalization with both strong and weak EWGs. In oneexample, a tin acetate precursor and phosphoric acid are used tosynthesize an AMO of tin. X-ray photoelectron spectroscopy analysis ofthe surface shows a greater atomic concentration of phosphorous than ofthe bonds associated with acetate groups (see FIG. 10).

Seventh, and last, while the disclosed method is a general procedure forsynthesis of AMOs, the synthesis procedures and conditions may beadjusted to yield sizes, morphologies, oxidation states, and crystallinestates as are deemed to be desirable for different applications. As oneexample, catalytic applications might desire an AMO material which ismore active in visible light (see FIG. 11A) or one which is more activein ultraviolet light (see FIG. 11B).

In another example, the AMO material may be used as a battery electrode.A primary (single-use) battery application might desire an AMO withcharacteristics that lead to the highest capacity, while a secondary(rechargeable) battery application might desire the same AMO but withcharacteristics that lead to the highest cyclability. FIG. 12 comparesthe cyclability of two different batteries constructed from AMOmaterials, including a chlorine containing AMO and a sulfur containingAMO. The AMO material can result in enhanced battery performance,without deterioration of battery components or gas generation (see FIG.13). This is exactly opposite what the prior art teaches.

In FIG. 13, the charge-discharge cyclability of a battery constructed asa half-cell of an AMO nanomaterial electrode versus lithium metal isshown, showing cyclability for up to 900 charge-discharge cycles, whilestill maintaining useful capacity and exceptional columbic efficiency.Such long cyclability is exceptional, particularly against the lithiummetal reference electrode, as lithium metal is known to grow dendritesduring even low cycle numbers, which can enlarge and result in dangerousand catastrophic failure of a battery cell.

According to the present disclosure, in a complete cell, the anode 106comprising the disclosed AMO may be utilized with a known electrolyte108 and a cathode 104 comprising known materials such as lithium cobaltoxide (LiCoO2). The material comprising the separator 110 may likewisebe drawn from those currently known in the art.

In a complete cell, the cathode 104 comprising the disclosed AMO may beutilized with a known electrolyte 108 and an anode 106 comprising knownmaterials such as carbon on copper foil, which display lesselectronegativity than AMO's of the present disclosure. The materialcomprising the separator 110 and electrolyte 108 may likewise be drawnfrom those currently known in the art as discussed above.

Various layering and other enhancement techniques may be deployed tomaximize capacity for holding lithium ions for powering the cell 100. Itshould also be understood that a battery based on an AMO cathode 104according to the present disclosure can be deployed as a secondary(e.g., rechargeable) battery but can also serve as a primary battery.Although the AMO anodes of the present disclosure lend themselves to areversible battery chemistry, a cell or battery constructed as describedherein, may be satisfactorily deployed as a primary cell or battery.

In the battery industry, the word ‘formation’ is used to denote initialcharge or discharge of the battery carried out at the manufacturingfacility prior to the battery being made available for use. Theformation process is generally quite slow and may require multiplecycles directed at converting the active materials as-manufactured intoa form that is more usable for cell cycling. These conversions may bealterations of the structure, morphology, crystallinity, and/orstoichiometry of the active materials.

Cells and batteries constructed according to the present disclosure, insome embodiments, do not require initial formation and therefore areready to use as primary cells or batteries. In other cases, limited orrapid formation may be employed. Moreover, by deploying the cells andbatteries of the present disclosure as primary cells that are notintended to be recharged, some of the safety issues that may be inherentwith lithium battery chemistry are mitigated, as it is known in the artthat the safety issues more frequently arise during battery cycling.However, following an initial primary discharge, cells and batteriesdisclosed herein are optionally suitable for use as secondary batterysystems which may undergo many charge-discharge cycles, such as up totens, hundreds, or even thousands of cycles.

In other embodiments according to the present disclosure, the cathode104 comprises nanoparticles of tin oxide (SnO₂) but it has not beenacidified in accordance with the AMO's described above. Knownelectrolytes 108, anodes 106, and separators 110, or those otherwisedescribed in this disclosure may be utilized with such embodiments.

It will be appreciated that other battery constructions are possibleusing the AMO material. For example, a battery may comprise a firstelectrode comprising an AMO nanomaterial, a second electrode, and anelectrolyte positioned between the first electrode and the secondelectrode. As an example, in a lithium ion battery, the first electrodemay operate as a cathode or an anode. For example, in operation as acathode, the second electrode may correspond to lithium metal, graphite,or another anodic material. As another example, in operation as ananode, the second electrode may correspond to a LiCoO2, LiMn2O4, LiNiO2,or another cathodic material. Useful materials for the second electrodeinclude, but are not limited to, graphite, lithium metal, sodium metal,lithium cobalt oxide, lithium titanate, lithium manganese oxide, lithiumnickel manganese cobalt oxide (NMC), lithium iron phosphate, lithiumnickel cobalt aluminum oxide (NCA), or any combination of these.

It will be appreciated that the AMO materials disclosed herein may alsobe added as dopants to conventional lithium ion cell anodes and/orcathodes, such as in amounts between 0.01 wt. % and 10 wt. %, or forexample, an amount of about 1 wt. %, 5 wt. % or 10 wt. % of AMO materialin an electrode. The disclosed AMO materials provide an incrediblecapacity for storing lithium atoms and by adding these materials toconventional lithium ion cell electrodes, the ability of thesecomposite. As one specific example, an electrode comprises LiCoO2 and anAMO. As another example, an electrode comprises a carbonaceous material,such as graphite, and an AMO.

The AMO materials of the present disclosure may optionally be used withan acidic component, such as a binder, an acidic electrolyte, or anacidic electrolyte additive. This may be in the context of an anode,cathode, half-cell, complete cell, integrated battery, or othercomponents. The inventors have surprisingly found that including acidiccomponents and/or acidic species, such as organic acids or organic acidanhydrides, in a battery comprising an AMO material results in anincrease in the capacity of versus batteries where the acidic speciesare not included. Again, the prior art teaches against use of acidicspecies, as these species may degrade metal current collectors andhousings and cause deterioration in other electrode components.

As shown in FIG. 14, which provides comparative cyclability data forAMO-based batteries formed of the same materials and structure exceptfor one having a standard electrolyte, one having a basifiedelectrolyte, and one having an acidified electrolyte. The batteriesincluded a construction as follows: all cathodes included the same AMOmaterial; all anodes were lithium metal; the standard electrolyte was a1:1:1 mix of dimethylene carbonate, diethylene carbonate, and ethylenecarbonate with 1 M LiPF6; the acidified electrolyte was the standardelectrolyte with 3 wt. % succinic anhydride; the basified electrolytewas the standard electrolyte with 3 wt. % dimethylacetamide. Allbatteries were cycled at the same discharge rate. As illustrated, thebattery with the acidified electrolyte system exhibits the best cyclingability, maintaining the highest capacity over the largest number ofcycles.

FIG. 15 provides additional comparative cyclability data for twodifferent batteries with the same battery construction including anacidified electrolyte, except that the AMO material of one battery isdeacidified by washing with a solvent. The batteries included aconstruction as follows: the cathodes included the AMO material; theelectrolyte was a 1:1:1 mix of dimethylene carbonate, diethylenecarbonate, and ethylene carbonate with 1 M LiPF6 and 3 wt. % succinicanhydride; the anodes were lithium metal. The batteries were cycled atthe same discharge rate. The battery having the acidified AMO materialexhibits higher capacity retention vs. cycle number, indicating that theacidified surface of the AMO may interact with the acidifiedelectrolyte, providing enhanced performance.

Several acidic electrolytes have been developed and/or tested and beenfound to operate advantageously with the cell chemistry describedherein.

Example 1: AMO of Tin Oxide Functionalized by Acetate/Chloride

A tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution and acidified by addition of hydrochloric acid(HCl). The resultant AMO nanomaterial was a soft, grey material and wasformed into an electrode. The electrode was assembled in a battery cellagainst lithium metal and cycled by discharging to zero volts, followedby charging to 1.5 volts. FIG. 16 depicts a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 2: AMO of Tin Oxide Functionalized by Acetate/Sulfate

A tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution and acidified by addition of sulfuric acid(H2SO4). The resultant AMO nanomaterial was a grey, flaky material andwas formed into an electrode. The electrode was assembled in a batterycell against lithium metal and cycled by discharging to zero volts,followed by charging to 1.5 volts. FIG. 17 depicts an electronmicrograph image of the AMO nanomaterial, a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 3: AMO of Tin Oxide Functionalized By Acetate/Nitrate

A tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution and acidified by addition of nitric acid (HNO3).The resultant AMO nanomaterial was a grey, flaky material and was formedinto an electrode. The electrode was assembled in a battery cell againstlithium metal and cycled by discharging to zero volts, followed bycharging to 1.5 volts. FIG. 18 depicts an electron micrograph image ofthe AMO nanomaterial, a plot of the measured capacity versus cyclenumber, as well as a plot of the voltage as a function of time duringcycling.

Example 4: AMO of Tin Oxide Functionalized by Acetate/Phosphate

A tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution and acidified by addition of phosphoric acid(H3PO4). The resultant AMO nanomaterial was a brown, soft, flakymaterial and was formed into an electrode. The electrode was assembledin a battery cell against lithium metal and cycled by discharging tozero volts, followed by charging to 1.5 volts. FIG. 19 depicts anelectron micrograph image of the AMO nanomaterial, a plot of themeasured capacity versus cycle number, as well as a plot of the voltageas a function of time during cycling.

Example 5: AMO of Tin Oxide Functionalized by Acetate/Citrate

A tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution and acidified by addition of citric acid(C6H8O7). The resultant AMO nanomaterial was a brown, flaky material andwas formed into an electrode. The electrode was assembled in a batterycell against lithium metal and cycled by discharging to zero volts,followed by charging to 1.5 volts. FIG. 20 depicts a plot of themeasured capacity versus cycle number, as well as a plot of the voltageas a function of time during cycling.

Example 6: AMO of Tin Oxide Functionalized by Acetate/Citrate

A tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution and acidified by addition of oxalic acid(C2H2O4). The resultant AMO nanomaterial was a taupe, flaky material andwas formed into an electrode. The electrode was assembled in a batterycell against lithium metal and cycled by discharging to zero volts,followed by charging to 1.5 volts. FIG. 21 depicts a plot of themeasured capacity versus cycle number, as well as a plot of the voltageas a function of time during cycling.

Example 7: AMO OF Tin Oxide Doped with Iron Oxide and Functionalized byAcetate/Chloride

A doped tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution with a lesser amount of iron acetate. Thesolution was acidified by addition of hydrochloric acid (HCl). Theresultant AMO nanomaterial was a soft and flaky, creamy grey materialand was formed into an electrode. The electrode was assembled in abattery cell against lithium metal and cycled by discharging to zerovolts, followed by charging to 1.5 volts. FIG. 22 depicts an electronmicrograph image of the AMO nanomaterial, a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 8: AMO of Tin Oxide Doped with Iron Oxide and Functionalized byAcetate/Sulfate

A doped tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution with a lesser amount of iron acetate. Thesolution was acidified by addition of sulfuric acid (H2SO4). Theresultant AMO nanomaterial was a pale, taupe colored, soft, flakymaterial and was formed into an electrode. The electrode was assembledin a battery cell against lithium metal and cycled by discharging tozero volts, followed by charging to 1.5 volts. FIG. 23 depicts a plot ofthe measured capacity versus cycle number, as well as a plot of thevoltage as a function of time during cycling.

Example 9: AMO of Tin Oxide Doped with Iron Oxide and Functionalized byAcetate/Nitrate

Two doped tin oxide AMO samples were synthesized using a single-pothydrothermal synthesis method. Briefly, tin acetate (Sn(CH3COO)2) wasdissolved in an ethanol/water solution with a lesser amount of ironacetate (Fe(CH3COO)3). The solution was acidified by addition of nitricacid (HNO3). The resultant AMO nanomaterial was a soft, white materialand was formed into an electrode. The electrode was assembled in abattery cell against lithium metal and cycled by discharging to zerovolts, followed by charging to 1.5 volts. FIG. 24 depicts an electronmicrograph image of the AMO nanomaterial, a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 10: AMO of Tin Oxide Doped with Iron Oxide and Functionalized ByAcetate/Oxalate

A doped tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution with a lesser amount of iron acetate(Fe(CH3COO)3). The solution was acidified by addition of oxalic acid(C2H2O4). The resultant AMO nanomaterial was a soft, white material andwas formed into an electrode. The electrode was assembled in a batterycell against lithium metal and cycled by discharging to zero volts,followed by charging to 1.5 volts. FIG. 25 depicts an electronmicrograph image of the AMO nanomaterial, a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 11: AMO of Tin Oxide Doped with Iron Oxide and Functionalized byAcetate/Phosphate

A doped tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution with a lesser amount of iron acetate(Fe(CH3COO)3). The solution was acidified by addition of phosphoric acid(H3SO4). The resultant AMO nanomaterial was a white, flaky material andwas formed into an electrode. The electrode was assembled in a batterycell against lithium metal and cycled by discharging to zero volts,followed by charging to 1.5 volts. FIG. 26 depicts a plot of themeasured capacity versus cycle number, as well as a plot of the voltageas a function of time during cycling.

Example 12: Tin Oxide Doped with Iron Oxide and Functionalized byAcetate/Citrate

A doped tin oxide was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution with a lesser amount of iron acetate(Fe(CH3COO)3). The solution was acidified by addition of citric acid(C6H8O7). The resultant material did not form particles, and was ayellow, glassy hard material, which was formed into an electrode. Theelectrode was assembled in a battery cell against lithium metal andcycled by discharging to zero volts, followed by charging to 1.5 volts.FIG. 27 depicts an electron micrograph image of the AMO nanomaterial, aplot of the measured capacity versus cycle number, as well as a plot ofthe voltage as a function of time during cycling.

Example 13: AMO of Tin Oxide Functionalized by Acetate/Bromide

A tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution and acidified by addition of hydrobromic acid(HBr). The resultant AMO nanomaterial was a grey, soft, powdery materialand was formed into an electrode. The electrode was assembled in abattery cell against lithium metal and cycled by discharging to zerovolts, followed by charging to 1.5 volts. FIG. 28 depicts an electronmicrograph image of the AMO nanomaterial, a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 14: AMO of Tin Oxide Functionalized by Acetate/Borate

A tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin acetate (Sn(CH3COO)2) was dissolved in anethanol/water solution and acidified by addition of boric acid (H3BO3).The resultant AMO nanomaterial was a grey, flaky material and was formedinto an electrode. The electrode was assembled in a battery cell againstlithium metal and cycled by discharging to zero volts, followed bycharging to 1.5 volts. FIG. 29 depicts an electron micrograph image ofthe AMO nanomaterial, a plot of the measured capacity versus cyclenumber, as well as a plot of the voltage as a function of time duringcycling.

Example 15: AMO of Tin Oxide Doped with Manganese Oxide andFunctionalized by Sulfate/Chloride

A doped tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin sulfate (SnSO4) was dissolved in anethanol/water solution with a lesser amount of manganese chloride(MnCl2). The solution was acidified by addition of sulfuric acid(H2SO4). The resultant AMO nanomaterial was a very soft, tan materialand was formed into an electrode. The electrode was assembled in abattery cell against lithium metal and cycled by discharging to zerovolts, followed by charging to 1.5 volts. FIG. 30 depicts an electronmicrograph image of the AMO nanomaterial, a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 16: AMO of Tin Oxide Doped with Manganese Oxide andFunctionalized by Chloride

A doped tin oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, tin chloride (SnCl2) was dissolved in anethanol/water solution with a lesser amount of manganese chloride(MnCl2). The solution was acidified by addition of hydrochloric acid(HCl). The resultant AMO nanomaterial was a soft, greyish brown materialand was formed into an electrode. The electrode was assembled in abattery cell against lithium metal and cycled by discharging to zerovolts, followed by charging to 1.5 volts. FIG. 31 depicts an electronmicrograph image of the AMO nanomaterial, a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 17: AMO of Tin Oxide Doped with Iron Oxide and Aluminum Oxideand Functionalized by Chloride

Two doped tin oxide AMO samples were synthesized using a single-pothydrothermal synthesis method. Briefly, tin chloride (SnCl2) wasdissolved in an ethanol/water solution with lesser amounts of both ironchloride (FeCl3) and aluminum chloride (AlCl3). The solution wasacidified by addition of hydrochloric acid (HCl). The resultant AMOnanomaterial for the first sample was a light tan, flaky material andwas formed into an electrode. The electrode was assembled in a batterycell against lithium metal and cycled by discharging to zero volts,followed by charging to 1.5 volts. FIG. 32 depicts a plot of themeasured capacity versus cycle number, as well as a plot of the voltageas a function of time during cycling. The resultant AMO nanomaterial forthe second sample was a light grey, flaky material.

Example 18: AMO of Iron Oxide Doped with Tin Oxide and Functionalized byChloride

A doped iron oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, iron chloride (FeCl3) was dissolved in anethanol/water solution with a lesser amount of tin chloride (SnCl2). Theratio of iron to tin was 95:5. The solution was acidified by addition ofhydrochloric acid (HCl). The resultant AMO nanomaterial was a soft, redmaterial and was formed into an electrode. The electrode was assembledin a battery cell against lithium metal and cycled by discharging tozero volts, followed by charging to 1.5 volts. FIG. 33 depicts a plot ofthe measured capacity versus cycle number, as well as a plot of thevoltage as a function of time during cycling.

Example 19: AMO of Iron Oxide Doped with Tin Oxide and Functionalized byChloride

A doped iron oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, iron chloride (FeCl3) was dissolved in anethanol/water solution with a lesser amount of tin chloride (SnCl2). Theratio of iron to tin was 95:5. The solution was acidified by addition ofhydrochloric acid (HCl). The resultant AMO nanomaterial was a black,glassy material and was formed into an electrode. The electrode wasassembled in a battery cell against lithium metal and cycled bydischarging to zero volts, followed by charging to 1.5 volts. FIG. 34depicts a plot of the measured capacity versus cycle number, as well asa plot of the voltage as a function of time during cycling.

Example 20: AMO of Iron Oxide Functionalized by Nitrate

An iron oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, iron nitrate Fe(NO3)3 was dissolved in anethanol/water solution and acidified by addition of nitric acid (HNO3).The resultant AMO nanomaterial was a black, glassy material and wasformed into an electrode. The electrode was assembled in a battery cellagainst lithium metal and cycled by discharging to zero volts, followedby charging to 1.5 volts. FIG. 35 depicts a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 21: AMO of Bismuth Oxide Functionalized by Chloride

A bismuth oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, bismuth chloride (BiCl3) was dissolved in anethanol/water solution and acidified by addition of hydrochloric acid(HCl). The resultant AMO nanomaterial was a soft, white material and wasformed into an electrode. The electrode was assembled in a battery cellagainst lithium metal and cycled by discharging to zero volts, followedby charging to 1.5 volts. FIG. 36 depicts a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 22: AMO of Zirconium Oxide Functionalized by Sulfate

A zirconium oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, zirconium sulfate (Zr(SO4)2) was dissolved inan ethanol/water solution and acidified by addition of sulfuric acid(H2SO4). The resultant AMO nanomaterial was a flaky, white material andwas formed into an electrode. The electrode was assembled in a batterycell against lithium metal and cycled by discharging to zero volts,followed by charging to 1.5 volts. FIG. 37 depicts a plot of themeasured capacity versus cycle number, as well as a plot of the voltageas a function of time during cycling.

Example 23: AMO of Titanium Oxide Functionalized by Sulfate

A titanium oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, titanium oxysulfate (TiOSO4) was dissolved inan ethanol/water solution and acidified by addition of sulfuric acid(H2SO4). The resultant AMO nanomaterial was a white, flaky material andwas formed into an electrode. The electrode was assembled in a batterycell against lithium metal and cycled by discharging to zero volts,followed by charging to 1.5 volts. FIG. 38 depicts an electronmicrograph image of the AMO nanomaterial, a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 24: AMO of Antimony Oxide Functionalized by Sulfate

An antimony oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, antimony sulfate (Sb2(SO4)3) was dissolved inan ethanol/water solution and acidified by addition of sulfuric acid(H2SO4). The resultant AMO nanomaterial was a very soft, white materialand was formed into an electrode. The electrode was assembled in abattery cell against lithium metal and cycled by discharging to zerovolts, followed by charging to 1.5 volts. FIG. 39 depicts a plot of themeasured capacity versus cycle number, as well as a plot of the voltageas a function of time during cycling.

Example 25: AMO of Indium Oxide Functionalized by Chloride

An indium oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, indium chloride (InCl3) was dissolved in anethanol/water solution and acidified by addition of hydrochloric acid(HCl). The resultant AMO nanomaterial was a white material and wasformed into an electrode. The electrode was assembled in a battery cellagainst lithium metal and cycled by discharging to zero volts, followedby charging to 1.5 volts. FIG. 40 depicts an electron micrograph imageof the AMO nanomaterial, a plot of the measured capacity versus cyclenumber, as well as a plot of the voltage as a function of time duringcycling.

Example 26: AMO of Indium Oxide Functionalized by Sulfate

An indium oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, indium sulfate (In2(SO4)3) was dissolved inan ethanol/water solution and acidified by addition of sulfuric acid(H2SO4). The resultant AMO nanomaterial was a white material and wasformed into an electrode. The electrode was assembled in a battery cellagainst lithium metal and cycled by discharging to zero volts, followedby charging to 1.5 volts. FIG. 41 depicts an electron micrograph imageof the AMO nanomaterial, a plot of the measured capacity versus cyclenumber, as well as a plot of the voltage as a function of time duringcycling.

Example 27: AMO of Indium Oxide Functionalized by Bromide

An indium oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, indium bromide (InBr3) was dissolved in anethanol/water solution and acidified by addition of hydrobromic acid(HBr). The resultant AMO nanomaterial was a blue-white material and wasformed into an electrode. The electrode was assembled in a battery cellagainst lithium metal and cycled by discharging to zero volts, followedby charging to 1.5 volts. FIG. 42 depicts an electron micrograph imageof the AMO nanomaterial, a plot of the measured capacity versus cyclenumber, as well as a plot of the voltage as a function of time duringcycling.

Example 28: AMO of Indium Oxide Functionalized by Chloride

An indium oxide AMO was synthesized using a single-pot hydrothermalsynthesis method. Briefly, indium chloride (InCl3) was dissolved in anethanol/water solution and acidified by addition of hydrochloric acid(HCl). The resultant AMO nanomaterial was grey with a yellow ring andwas formed into an electrode. The electrode was assembled in a batterycell against lithium metal and cycled by discharging to zero volts,followed by charging to 1.5 volts. FIG. 43 depicts an electronmicrograph image of the AMO nanomaterial, a plot of the measuredcapacity versus cycle number, as well as a plot of the voltage as afunction of time during cycling.

Example 29: Mixed AMO of Lithium Oxide and Iron Oxide Doped with TinOxide and Functionalized by Chloride/Acetate

A doped mixed lithium oxide and iron oxide AMO was synthesized using asingle-pot hydrothermal synthesis method. Briefly, lithium acetate(Li(CH3COO)) and iron chloride (FeCl3) were dissolved in anethanol/water solution with a lesser amount of tin chloride (SnCl2). Thesolution was acidified by addition of hydrochloric acid (HCl). Duringsynthesis, a tan, pinkish color with a green ring on the flaskdeveloped. The final AMO nanomaterial, however, was grey and was formedinto an electrode. The electrode was assembled in a battery cell againstlithium metal and cycled by discharging to zero volts, followed bycharging to 1.5 volts. FIG. 44 depicts an electron micrograph image ofthe AMO nanomaterial, a plot of the measured capacity versus cyclenumber, as well as a plot of the voltage as a function of time duringcycling.

Example 30: Mixed AMO of Lithium Oxide and Iron Oxide Doped with TinOxide and Functionalized by Chloride/Acetate

A doped mixed lithium oxide and iron oxide AMO was synthesized using asingle-pot hydrothermal synthesis method. Briefly, lithium acetate(Li(CH3COO)) and iron chloride (FeCl3) were dissolved in anethanol/water solution with a lesser amount of tin chloride (SnCl2). Thesolution was acidified by addition of hydrochloric acid (HCl). Theresultant AMO nanomaterial was a golden pale material and was formedinto an electrode. The electrode was assembled in a battery cell againstlithium metal and cycled by discharging to zero volts, followed bycharging to 1.5 volts. FIG. 45 depicts an electron micrograph image ofthe AMO nanomaterial, a plot of the measured capacity versus cyclenumber, as well as a plot of the voltage as a function of time duringcycling.

Example 31: Mixed AMO of Lithium Oxide and Iron Oxide Doped with TinOxide and Functionalized by Chloride/Acetate

A doped mixed lithium oxide and iron oxide AMO was synthesized using asingle-pot hydrothermal synthesis method. Briefly, lithium acetate(Li(CH3COO)) and iron chloride (FeCl3) were dissolved in anethanol/water solution with a lesser amount of tin chloride (SnCl2). Thesolution was acidified by addition of hydrochloric acid (HCl). Theresultant AMO nanomaterial was a light creamy white material and wasformed into an electrode. The electrode was assembled in a battery cellagainst lithium metal and cycled by discharging to zero volts, followedby charging to 1.5 volts. FIG. 46 depicts an electron micrograph imageof the AMO nanomaterial, a plot of the measured capacity versus cyclenumber, as well as a plot of the voltage as a function of time duringcycling.

At the present time, lithium batteries are perceived to be a safety riskin certain situations. For example, airline regulations currentlyrequire partial discharge of lithium batteries that are to be carried inthe cargo hold. Fires have been reported in devices utilizing lithiumbatteries resultant from runaway exothermal reactions. Moreover, lithiumfires can be difficult to extinguish with popularly deployed firesuppression systems and devices. For these reasons, lithium containingcompounds rather than metallic lithium is used in many commercialbattery cells.

Use of lithium containing compounds in an anode, rather than lithiummetal, may, however, limit the amount of lithium available for reactionand incorporation into the cathode upon discharge, and may thus alsolimit the capacity of such cells. The presently disclosed AMO materials,however, show not only large uptake of lithium during discharge but alsoenhanced safety characteristics. For example, when battery cellscomprising the AMO material in a cathode and a lithium metal electrodeare subjected to safety tests, such as nail penetration tests, shortingtests, and overvoltage tests, the cells perform well and do not appearto pose an unacceptable risk of fire or explosion. This may be becausethe AMO's passivate lithium metal within a cell or battery. Even usingsolid or pure lithium as an anode, devices employing AMO's of thepresent disclosure as a cathode do not appear to pose an unacceptablerisk of fire or explosion. The novel safety results may also be due tothe low operating voltage of cells constructed according to the presentdisclosure, which in some embodiments is <1.5 V compared to atraditional lithium ion operating voltage of >3.0 V.

Several cells were constructed with a cathode comprising an AMO (SnO₂)according to the present disclosure. The cathode was prepared from acomposition of the AMO (SnO₂), Ketjen black (KB), polyvinylidenefluouride (PVDF), and polyaryl amide (PAA) at a ratio of 63/10/26.1/0.9by volume. Double-sided layers of this composition were prepared at 4mg/cm² per side. Six of these layers comprised the cathode. The area ofthe prepared cathode was 9×4 cm². A separator was obtained from TargrayTechnology International, Inc. and comprised a 25 μm thick layer ofpolypropylene. The separator was 9.4×4.4 cm² in area. An electrolyte wasprepared from 1 M LiPF₆ in a solvent of ethylene carbonate, diethylcarbonate, and dimethyl carbonate in a 1/1/1 ratio by volume. The anodewas a 50 μm thick layer of lithium metal of 9.2×4.2 cm² in area.

Two of the constructed cells were discharged prior to a safety test andfound to have an actual capacity of 1.7 Ah, and a specific capacity of1575 mAh/g SnO₂.

FIG. 47 is a plot of temperature and voltage for a cell constructed asdescribed above and subjected to a nail penetration test. The test wasconducted at room temperature and no events (e.g., fires) were observed.It can also be seen that the temperature and voltage remained stable.

FIG. 48A is a plot of temperature and voltage for a cell constructed asdescribed above and subjected to an overcharge test. A 1 A current wasapplied. Apart from some gassing from the cell no adverse events wereobserved over the timeframe of the test. FIG. 48B is a plot of theovercharge test of FIG. 48A focusing on the start of the test.

It should be understood that the examples constructed for purpose ofpenetration tests are not intended to be limiting with respect to theentire disclosure herein. Cells and batteries of various sizes,capacities, and materials may be constructed according to the presentdisclosure. Utilizing the AMO's of the present disclosure, suchbatteries would reap the benefits of the increased safety demonstratedherein, whether such safety is ultimately due to lithium passivation,lower voltage, or other factors.

Embodiments of constructed electrochemical cells incorporating AMOmaterial as a cathode and lithium as an electrode have been tested tosuccessfully undergo up to 900 or more charge-discharge cycles withoutresulting in catastrophic and destructive failure. Stated another way,embodiments of constructed electrochemical cells incorporating AMOmaterial as a cathode and lithium as an electrode have been tested tosuccessfully undergo up to 900 or more charge-discharge cycles and stillhold a charge and maintain useful capacity.

Without wishing to be bound by any theory, the enhanced safety providedby use of AMO-based cathode materials in lithium cells may arise fromthe ability of the AMO material to passivate metallic lithium andprevent dendrite formation. The inventors have observed that, uponcycling, the metallic lithium anode did not appear to grow or otherwiseform dendrites, but the lithium anode took on a softer and lesscrystalline appearing structure. In some embodiments, the lithium anodemay be passivated, such as by cycling as a component of anelectrochemical cell as described herein, and then removed from theelectrochemical cell and used as an electrode in a new electrochemicalcell with a different cathode. Additionally, cells constructed accordingto the present disclosure make use of low operating voltages, such asbetween 1 and 2 volts, which contrasts with the typical voltage of alithium or lithium-ion battery cell, which operate commonly around 3-4.2volts. Such a difference in operational voltage may, in part, accountfor the safety of the disclosed cells.

With respect to construction of cells or batteries using lithium as ananode according to the present disclosure, in some embodiments, theentire anode (100%) is metallic lithium. The metallic lithium may onlybe substantially pure in that a minute percentage of the anode maycomprise trace elements and impurities that do not affect theperformance of the cell or battery in a measurable way. In variousembodiments, the anode comprises at least 50%, 55%, 60%, 65%, 75%, 80%,85%, 90%, or 95% metallic lithium.

For purposes of the present disclosure the term “metallic lithium”refers to lithium in its neutral atomic state (i.e., non-ionic state).The term metallic lithium is intended to distinguish over other forms oflithium including lithium ions and lithium compounds. The term metalliclithium may refer to neutral atomic lithium present in mixtures thatcomprise lithium atoms, such as mixtures of lithium and other elements,compounds, or substances. The term metallic lithium may refer to neutralatomic lithium present in lithium alloys, such as a metallic mixtureincluding lithium and one or more other metals. The term metalliclithium may refer to neutral atomic lithium present in compositestructures including lithium and one or more other materials. Electrodescomprising or including metallic lithium may include other materialsbesides lithium, but it will be appreciated that metallic lithium maycorrespond to an active material of such an electrode. In some cases, ananode in an electrochemical cell comprises metallic lithium.

For purposes of this disclosure, metallic lithium may be taken to meanlithium that is not reacted with any other element so as to have formeda compound (at least at the time of battery or cell construction). Insome embodiments, a portion of the anode may be metallic lithium while aportion of the anode may be a lithium compound containing variouspercentages of lithium that is reacted with other elements to form alithium compound. The metallic lithium may be arranged to be segregatedgeometrically on or in the anode relative to the lithium compoundportion of the anode.

All references throughout this application, for example patent documentsincluding issued or granted patents or equivalents, patent applicationpublications, and non-patent literature documents or other sourcematerial, are hereby incorporated by reference herein in theirentireties, as though individually incorporated by reference.

All patents and publications mentioned in the specification areindicative of the levels of skill of those skilled in the art to whichthe invention pertains. References cited herein are incorporated byreference herein in their entirety to indicate the state of the art, insome cases as of their filing date, and it is intended that thisinformation can be employed herein, if needed, to exclude (for example,to disclaim) specific embodiments that are in the prior art. Forexample, when a compound is claimed, it should be understood thatcompounds known in the prior art, including certain compounds disclosedin the references disclosed herein (particularly in referenced patentdocuments), are not intended to be included in the claim.

When a group of substituents is disclosed herein, it is understood thatall individual members of those groups and all subgroups and classesthat can be formed using the substituents are disclosed separately. Whena Markush group or other grouping is used herein, all individual membersof the group and all combinations and subcombinations possible of thegroup are individually included in the disclosure. As used herein,“and/or” means that one, all, or any combination of items in a listseparated by “and/or” are included in the list; for example “1, 2 and/or3” is equivalent to “‘1’ or ‘2’ or ‘3’ or ‘1 and 2’ or ‘1 and 3’ or ‘2and 3’ or ‘1, 2 and 3’”.

Every formulation or combination of components described or exemplifiedcan be used to practice the invention, unless otherwise stated. Specificnames of materials are intended to be exemplary, as it is known that oneof ordinary skill in the art can name the same material differently. Oneof ordinary skill in the art will appreciate that methods, deviceelements, starting materials, and synthetic methods other than thosespecifically exemplified can be employed in the practice of theinvention without resort to undue experimentation. All art-knownfunctional equivalents, of any such methods, device elements, startingmaterials, and synthetic methods are intended to be included in thisinvention. Whenever a range is given in the specification, for example,a temperature range, a time range, or a composition range, allintermediate ranges and subranges, as well as all individual valuesincluded in the ranges given are intended to be included in thedisclosure.

As used herein, “comprising” is synonymous with “including,”“containing,” or “characterized by,” and is inclusive or open-ended anddoes not exclude additional, unrecited elements or method steps. As usedherein, “consisting of” excludes any element, step, or ingredient notspecified in the claim element. As used herein, “consisting essentiallyof” does not exclude materials or steps that do not materially affectthe basic and novel characteristics of the claim. Any recitation hereinof the term “comprising,” particularly in a description of components ofa composition or in a description of elements of a device, is understoodto encompass those compositions and methods consisting essentially ofand consisting of the recited components or elements. The inventionillustratively described herein suitably may be practiced in the absenceof any element or limitation that is not specifically disclosed herein.

The terms and expressions which have been employed are used as terms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed. Thus, it should be understood that although thepresent invention has been specifically disclosed by preferredembodiments and optional features, modification and variation of theconcepts herein disclosed may be resorted to by those skilled in theart, and that such modifications and variations are considered to bewithin the scope of this invention as defined by the claims.

What is claimed:
 1. A battery cell comprising an anode, an electrolyte,and a cathode, wherein one of the anode or cathode comprises at leastone solid metal oxide nanomaterial including a surface that is acidicbut not superacidic, the surface having a pH<5 when re-suspended, afterdrying, in water at 5 wt % and a Hammet function H₀>−12, and wherein atleast part of the anode consists of metallic lithium.
 2. The batterycell of claim 1, wherein the solid metal oxide nanomaterial has at leastone particle dimension <100 nm in size.
 3. The battery cell of claim 1,wherein the solid metal oxide nanomaterial has at least one particledimension <20 nm in size.
 4. The battery cell of claim 1, wherein thesolid metal oxide nanomaterial has at least one particle dimension <10nm in size.
 5. The battery cell of claim 1, wherein the solid metaloxide nanomaterial includes a substantially monodispersednanoparticulate form.
 6. The battery cell of claim 1, wherein thesurface has a pH<4 when re-suspended, after drying, in water at 5 wt %and a Hammet function H₀>−12.
 7. The battery cell of claim 1, whereinthe surface has a pH<3 when re-suspended, after drying, in water at 5 wt% and a Hammet function H₀>−12.